(1) Field of the Invention
The present invention pertains to a load supporting device for use with conventional wheelchair frames. More particularly, the present invention pertains to a wheelchair seat or back rest which is adjustable laterally and longitudinally to fit most conventional wheelchair frames and to accommodate different sized wheelchair patients.
(2) Description of the Related Art
In a conventional wheelchair, a soft "sling" type seat is suspended between spaced apart rails of the wheelchair frame for supporting the weight of the wheelchair user. Similarly, many conventional wheelchairs use "sling" type upholstery for the wheelchair back rest. However, these soft "sling" type wheelchair seats or back rests can aggravate many of the health problems suffered by wheelchair users.
Persons who use wheelchairs for extended periods of time may require the use of inflatable wheelchair seat cushions to prevent the formation of decubitus ulcers. Inflatable wheelchair cushions, such as the one disclosed in co-assigned U.S. Pat. No. 5,561,875, serve to distribute the weight of the supported body evenly over the area of the body that is in contact with the cushion. The inflatable cushions are generally placed on top of the wheel chair seat. However, the effectiveness of such inflatable cushions is significantly diminished by the curved configuration of a conventional "sling" type wheelchair seat. Moreover, by stacking an inflatable cushion on top of the "sling" seat, the effective seat height is raised an amount equal to the thickness of the inflatable cushion. This may result in the patient not being able to properly reach the foot plates of the wheelchair. It also raises the center of gravity of the patient.
Attempts have been made to replace the "sling" type wheelchair seat with a flat, rigid seat base which can be suspended low enough between the spaced apart rails of the wheelchair frame to accommodate the thickness of an inflatable cushion. For example, U.S. Pat. No. 4,629,246 of Fulton discloses a rigid wheelchair seat base which is hook mounted onto a wheelchair frame. The seat base can be easily removed to facilitate collapsing of the wheelchair for transportation and storage. However, the seat base disclosed in the Fulton patent is not, under normal circumstances, size-adjustable. Consequently, the seat base must be custom constructed for each individual wheelchair and wheelchair user. This can become expensive, even for a single wheelchair user who may require different seat bases as his or her physical needs change over time.
More recently, attempts have been made to provide size-adjustable wheelchair seat bases which can be adjusted to fit a variety of wheelchair frames and to accommodate the current and changing needs of the wheelchair user. For example, U.S. Pat. No. 5,074,620 of Jay et al. discloses a wheelchair seat base which may be adapted to fit a variety of wheelchair frames and which is adjustable to fit different sized users. However, the means for adjusting the length and width of the seat are quite cumbersome and require the use of tools to accomplish any size adjustment. Moreover, the size-adjustment means are rather limited with the seat base being capable of only a few different sizes.